At the suggestion of my brother, I did a Megatherium,
or Giant Ground Sloth. Now, technically, Megatherium's not a Tertiary, because he came later (in the Quaternary). But what
the hey. He's a good addition to the group, and was the first bipedal mammal I did in the series.

Like so many of these guys (to me, anyhow), Megatherium was a cartoon
character. He really was a living caricature. To me, Megatheriums always looked like a cross between a bear and a giant kangaroo.
They lived in the Ice Age, alongside the Mammoths and Mastodons.